Physics
The working of the quartz crystal in the watch is based on the

Edison Effect
Johnson Effect
Piezo - electric Effect
Photoelectric Effect

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Physics
The bats can fly in the dark because

They have weak legs and are likely to be attacked by predators
They can see the objects in darkness
They generate flashes of light
They generate ultrasonic sound waves

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Physics
Absolute Zero is defined as

At which the volume becomes zero
At which liquid Helium boils
At which water boils at 298K
The temperature at which all molecular motion ceases

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